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High-Efficiency Radiation-Hard Solar Array Interface to Spacecraft Power System



TECHNOLOGY AREA(S): Space Platforms

OBJECTIVE: Develop concepts for a high efficiency, compact radiation hard interface between the solar array and the spacecraft power system

DESCRIPTION: Present state of the art power processing of electric power from spacecraft solar arrays utilizes a partial shunt strategy, string switching, or both to control the output of a solar array. The spacecraft solar array can degrade from 20% to 50% in power producing capability over a 15-year mission depending upon the specific orbit it must operate in. These schemes have worked well for solar arrays, which are sized for end of spacecraft life conditions.

However, these designs make it impossible to access the full power available from the solar array. The reason for this is that the solar array must be designed to deliver full power at end of life while being connected to a regulated spacecraft power system bus or a spacecraft battery with an unregulated spacecraft power system bus. In either case the solar array operation cannot be optimized to operate at peak power conditions. To date there have not been many spacecraft with loads which require power above end of life conditions.

However, with the advent of the use of electric propulsion for orbit raising the additional power that the solar array could deliver could reduce trip time from low earth orbit to the operational orbit of the satellite.

To solve this problem the solar array interface must be capable of delivering all of solar array power at the spacecraft bus voltage at beginning of life and end of life conditions. Potential methods for addressing this challenge include, but are not limited to; higher efficiency cell designs, alternate cellular arrangements, dynamic topology adjustment, high-efficiency reconfigurable charge management circuitry, concepts in soft-defined power-aware and degradation-aware distribution architecture possibilities.

The solar array interface should be capable of operation in a Low Earth Orbit (LEO) for 5 years and in a Geosynchronous Earth Orbit (GEO) or Medium Earth Orbit (MEO) for 15 years after storage on the ground for 5 years. It should function after 500 kRad (Si) total dose, be immune to dose rate and single event latchup, and not upset at a single event LET lower than 20 Mev/mg/cm2.

PHASE I: Perform preliminary analysis and conduct trade studies to validate performance for the solar array interface. Using breadboard hardware verify related performance information in support payoff estimates.

PHASE II: Fabricate and deliver engineering demonstration unit. Show the flexibility of delivering reliable power with the solar array at various load points. Identify radiation impacts upon components of the string converter.

PHASE III DUAL USE APPLICATIONS: Technology developed will be applicable to all military and commercial space platforms. Expected benefits include 20% to 50% increase in beginning of life solar array power.


  • Edward J. Simburger, Simon Liu, John Halpine, David Hinkley, J. R. Srour, and Daniel Rumsey, The Aerospace Corporation and Henry Yoo, Air Force Research Laboratory, Pico Satellite Solar Cell Testbed (PSSC Testbed), Presented at the 4th World Conference on Photovoltaic Energy Conversion, Wailoloa, Hawaii. May 7-12, 2006.
  • Edward J. Simburger, Daniel Rumsey, David Hinkley, Simon Liu and Peter Carian, The Aerospace Corporation, Distributed Power System for Microsatellites, 31st IEEE Photovoltaic Specialists Conference, Lake Buena Vista, FL. 3-7, January, 2005.
  • Kasemsan Siri and Calvin Truong, “Performance Limitations of random Current-Sharing Parallel-Connected Converter Systems & Their Solution,” APEC'98, Anaheim, California, pp. 860-866, Vol 2, February 14-19, 1998.
  • Kasemsan Siri, “Study of System Instability in Current-Mode Converter Power Systems Operating in Solar Array Voltage Regulation Mode,” APEC’2000, New Orleans, Louisiana, pp.228-234, Vol 1, February 6-10, 2000.
  • Kasemsan Siri, Vahe A. Caliskan and C.Q. Lee, "Maximum power tracking in parallel-connected converter systems," IEEE Trans. on Aerospace and Electronics Systems, vol. 29, no. 3, pp. 935-945, July 1993.

KEYWORDS: Peak Power Tracker, Solar Array, Parallel Power Conversion, Distribution and Control, Solar Array Regulation

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